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Old 11-02-2021, 05:56 PM
Stefannebula (Stefan)
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Complications of imaging near celestial pole?

Hi!

I would love to image an object that is close to the south celestial pole.

The object is Cederblad 111 and is only 12 degrees away from the SCP from my location.

I've never shot anything so close to the pole so I'm not sure if there are any complications that I'm not aware of. Perhaps I need a really tight polar alignment, or are there issues pointing in that location?

I will be using an NEQ6-Pro EQ mount with guiding and a scope with 420mm FL.

Would love to hear from someone with experience.
Thanks in advance!
Stefan
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Old 11-02-2021, 06:17 PM
RyanJones
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Hi Stephan

Imagining near the celestial pole is infact easier ( less demanding ) on your equipment. As your RA rotates the OTA has less apparent motion across the sky if that makes sense. An example is if you hold your arm out to the side and rotate across your body, the tips of your fingers have to move quite fast relative to your shoulder. If you now point out in front of you and rotate in an arc you hand moves much slower to cover the same angle of motion in the same amount of time. In this case when your OTA is pointing close to the pole there is significantly less inertia in the RA rotation making it much easier for your mount to correct for errors. Typically my guiding numbers are about 30% better close to the pole than close to the celestial equator. Hope this helps

Ryan
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Old 11-02-2021, 06:20 PM
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Rerouter (Ryan)
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The closer you get to the pole the looser the tracking requirements get, as everything is moving slower, e.g. with a Canon 600d you could image for up to 2 seconds without any tracking at all at that declination,

You will still want a decent polar alignment, but the length of the star trails will be shorter than if it was lower,

Main thing pointing that high up is making sure your scope doesn't hit anything while imaging, as that tends to put the camera low on refractors,
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Old 11-02-2021, 06:57 PM
RyanJones
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Quote:
Originally Posted by Rerouter View Post

Main thing pointing that high up is making sure your scope doesn't hit anything while imaging, as that tends to put the camera low on refractors,
The pole not the equator. The pole is low the equator is high.
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Old 11-02-2021, 07:04 PM
Startrek (Martin)
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Quote:
Originally Posted by Rerouter View Post
The closer you get to the pole the looser the tracking requirements get, as everything is moving slower, e.g. with a Canon 600d you could image for up to 2 seconds without any tracking at all at that declination,

You will still want a decent polar alignment, but the length of the star trails will be shorter than if it was lower,

Main thing pointing that high up is making sure your scope doesn't hit anything while imaging, as that tends to put the camera low on refractors,
The south celestial pole ( SCP ) or “the Pole” in Sydney is only around 34degrees in altitude
Not exactly “high”. In fact I would say most astrophotographers image above 35 degrees due to variations in atmospheric instability which affects your image quality and resolution , the severity of which depends on your image scale
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Old 11-02-2021, 07:05 PM
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Nikolas (Nik)
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My best tracking figures and also unguided images are always close to the poles. 10 minutes unguided on the Chicken for example.
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Old 11-02-2021, 07:09 PM
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multiweb (Marc)
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Quote:
Originally Posted by Stefannebula View Post
Hi!

I would love to image an object that is close to the south celestial pole.

The object is Cederblad 111 and is only 12 degrees away from the SCP from my location.

I've never shot anything so close to the pole so I'm not sure if there are any complications that I'm not aware of. Perhaps I need a really tight polar alignment, or are there issues pointing in that location?

I will be using an NEQ6-Pro EQ mount with guiding and a scope with 420mm FL.

Would love to hear from someone with experience.
Thanks in advance!
Stefan
Usually guiding is easier but polar alignment becomes more important so is balance.
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Old 11-02-2021, 08:03 PM
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The_bluester (Paul)
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The biggest wrinkle I have found in imaging near the pole is mosaics, usually I have found that camera clearance is better than nearly anywhere else and as others have indicated, guiding is generally easier.

Some mosaic planners fall to bits near the pole as your "Apparent" camera angle changes significantly as you move around in RA and the closer you are to the pole the worse it gets, you can end up with some "unexpected" results.
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Old 12-02-2021, 08:53 AM
jahnpahwa (JP)
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I'm excited to see what you come up with, Stefan

Great target, I might give it a go, too.
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  #10  
Old 13-02-2021, 11:21 AM
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The_bluester (Paul)
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I just had a look on Stellarium myself, I might have a go at it too if I ever get any clear sky, it is in a good spot for me now and would tide me over til my next planned target, which will be in a much better position next month.
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  #11  
Old 23-02-2021, 05:49 PM
Stefannebula (Stefan)
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Thanks, everyone for the advice! I ended up getting one night on this target, and just as you all said my tracking was the best I've seen with my current setup!

Hope you enjoy the picture, I highly recommend more people try to image CED 111 it's such an interesting region with so much going on!
I want to add another night's worth on this target to improve it, only got 1h each R,G,B and 2.5h L

Full Res: https://www.astrobin.com/full/1qezsg/0/

Cheers,
Stefan
Attached Thumbnails
Click for full-size image (CED_111_LRGB_5hSmall.jpg)
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  #12  
Old 25-02-2021, 08:33 AM
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multiweb (Marc)
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Beautiful
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  #13  
Old 26-02-2021, 04:20 PM
AdamJL
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yeah that's a beauty, Stefan, well done!
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  #14  
Old 26-02-2021, 06:37 PM
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That's a lovely image Stefan.

Greg.
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